The Center for Clinical Epidemiology and Biostatistics (CCEB) and the Center for Pharmacoepidemiology Research and Training (CPeRT) of the University of Pennsylvania (Penn) Perelman School of Medicine submit this renewal application to continue and expand our innovative and highly successful post-doctoral training program in clinical pharmacoepidemiology. Pharmacoepidemiology is the study of the use and effects of medications and other medical products in populations. This training program attracts highly qualified trainees from across the nation. This intensive two- to three-year intensive clinical research training program is designed to: 1) train clinicians to be rigorous and independent academic investigators able to formulate research questions and use a wide range of pharmacoepidemiologic approaches to answer those questions; 2) provide an understanding of the basic principles of clinical pharmacology; 3) provide intensive, supervised research experience with mentors in clinical pharmacoepidemiology and content-area mentors; and 4) strengthen the links between clinical epidemiology and clinical pharmacology. Trainees matriculate in our highly-successful Master of Science in Clinical Epidemiology (MSCE) degree program, and complete required courses in clinical epidemiology, pharmacoepidemiology research methods, outcome measurement, biostatistics, database management, pharmacokinetics; elective courses in drug development, pharmacology and other areas relevant to the trainees' interests and experience; independent readings; participation in research seminars at the CCEB and CPeRT; and the completion of a mentored independent research project of the trainee's design. Given the high demand for slots in this program, we propose to expand this program to support five fellows per year. Strengths of the proposed program include: 1) the large pool of highly qualified candidates with clinical training seeking rigorous research training in pharmacoepidemiology; 2) the long history of successful research training programs in the CCEB, including in pharmacoepidemiology and comparative effectiveness research / patient centered outcomes research; 3) the comprehensive course offerings and research programs available to trainees; and 4) the successful training record of the program director and other faculty. In addition, the availability of the CCEB and CPeRT faculty, who provide expertise in a wide range of methodologic and clinical disciplines; numerous epidemiologic databases useful for research projects and training; a broad array of specialized analytic capabilities available for clinical studies (e.g., clinical trials, case-contrl, cohort, self- controlled designs, etc.); and the faculty members' commitment to collaborative research and training, combine to provide an ideal environment for this program.